468 The Phylogeny of the Palmar Museculature 
branches for the muscles inserted into the fifth digit and the ulnar 
side of the fourth. 
The position of the main stems of the two nerves is therefore in 
the interval between the flexores breves profundi and the flexores breves 
medii, and there are consequently in the Urodeles two layers of muscles 
superficial (volar) to the nerves, namely, the flexor brevis medius and 
the flexor brevis superficialis, and two dorsal to them, namely, the 
flexor brevis profundus and the intermetacarpales. 
For the separation of the layers of each of these pairs no assistance 
is obtainable from the nerves, but in the case of the volar pair the sepa- 
ration is clearly indicated by the deeper layer of the palmar aponeu- 
rosis, while the position and direction of the intermetacarpales render 
them readily distinguishable from the flexores breves profundi. 
Fig. 3. Transverse section through the hand of Liolepisma laterale. fbms, super- 
ficial layer of the flexor brevis medius; fbm,,, middle layer of the flexor brevis 
medius; fbm,, deep layer of the flexor brevis medius; fbpq, muscles of the flexor 
brevis profundus which insert into their own digits; fbp,, muscles of the flexor 
brevi profundus which insert into adjacent digits; im, ligaments representing the 
intermetacarpales; p, palmar aponeurosis which gives rise to the deep tendons to 
the digits. 
II. THe Muscites or tHe REPTILIAN HAND. 
I have studied the hand muscles of the lacertilia from serial sections 
of Liolepisma laterale and Callisaurus draconoides and also by dissection 
of a fully grown specimen of Iguana tuberculata Gray, opportunity for 
the examination of the last having been afforded by the courtesy of 
my colleague, Professor J. E. Reighard. The dissection of the iguana 
proved to be of very great assistance in elucidating the extremely com- 
plicated appearances presented by the transverse sections of the other 
